Impact of multiple-frequency heating on the formation and control of diamagnetic electron rings in an axisymmetric mirror

Publisher Website
Google Scholar
Abstract
High‐beta, hot‐electron plasmas have been produced by electron‐cyclotron heating in the SM‐1 axisymmetric mirror using closely‐spaced multiple frequencies. The relativistic electrons produce annular distributions (ELMO rings) with as much as ten times more stored energy than with single‐frequency heating. While larger frequency separations (Δf/f∼0.1) provide some control of the ring size, the dominant effects are associated with an improvement in heating efficiency which persists to very small frequency separations (Δf/f∼10−3). Details of the reconstruction of the ring distribution (both in steady state and during build‐up), the influence of multiple frequency heating on fluctuations, axial electron losses, and a scaling of these effects with power are presented.